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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/hashbrown-0.12.3/src/macros.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>macros.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../normalize.css"><link rel="stylesheet" href="../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../ayu.css" disabled><link rel="stylesheet" href="../../dark.css" disabled><link rel="stylesheet" href="../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../storage.js"></script><script defer src="../../source-script.js"></script><script defer src="../../source-files.js"></script><script defer src="../../main.js"></script><noscript><link rel="stylesheet" href="../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../hashbrown/index.html"><div class="logo-container"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../hashbrown/index.html"><img class="rust-logo" src="../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span>
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</pre><pre class="rust"><code><span class="comment">// See the cfg-if crate.
</span><span class="attribute">#[allow(unused_macro_rules)]
</span><span class="macro">macro_rules! </span>cfg_if {
<span class="comment">// match if/else chains with a final `else`
</span>($(
<span class="kw">if </span><span class="attribute">#[cfg($(<span class="macro-nonterminal">$meta</span>:meta),<span class="kw-2">*</span>)] </span>{ $(<span class="macro-nonterminal">$it</span>:item)* }
) <span class="kw">else </span>* <span class="kw">else </span>{
$(<span class="macro-nonterminal">$it2</span>:item)*
}) =&gt; {
<span class="macro">cfg_if! </span>{
@__items
() ;
$( ( ($(<span class="macro-nonterminal">$meta</span>),<span class="kw-2">*</span>) ($(<span class="macro-nonterminal">$it</span>)<span class="kw-2">*</span>) ), )*
( () ($(<span class="macro-nonterminal">$it2</span>)<span class="kw-2">*</span>) ),
}
};
<span class="comment">// match if/else chains lacking a final `else`
</span>(
<span class="kw">if </span><span class="attribute">#[cfg($(<span class="macro-nonterminal">$i_met</span>:meta),<span class="kw-2">*</span>)] </span>{ $(<span class="macro-nonterminal">$i_it</span>:item)* }
$(
<span class="kw">else if </span><span class="attribute">#[cfg($(<span class="macro-nonterminal">$e_met</span>:meta),<span class="kw-2">*</span>)] </span>{ $(<span class="macro-nonterminal">$e_it</span>:item)* }
)*
) =&gt; {
<span class="macro">cfg_if! </span>{
@__items
() ;
( ($(<span class="macro-nonterminal">$i_met</span>),<span class="kw-2">*</span>) ($(<span class="macro-nonterminal">$i_it</span>)<span class="kw-2">*</span>) ),
$( ( ($(<span class="macro-nonterminal">$e_met</span>),<span class="kw-2">*</span>) ($(<span class="macro-nonterminal">$e_it</span>)<span class="kw-2">*</span>) ), )*
( () () ),
}
};
<span class="comment">// Internal and recursive macro to emit all the items
//
// Collects all the negated cfgs in a list at the beginning and after the
// semicolon is all the remaining items
</span>(@__items ($(<span class="macro-nonterminal">$not</span>:meta,)<span class="kw-2">*</span>) ; ) =&gt; {};
(@__items ($(<span class="macro-nonterminal">$not</span>:meta,)<span class="kw-2">*</span>) ; ( ($(<span class="macro-nonterminal">$m</span>:meta),<span class="kw-2">*</span>) ($(<span class="macro-nonterminal">$it</span>:item)<span class="kw-2">*</span>) ), $(<span class="macro-nonterminal">$rest</span>:tt)<span class="kw-2">*</span>) =&gt; {
<span class="comment">// Emit all items within one block, applying an approprate #[cfg]. The
// #[cfg] will require all `$m` matchers specified and must also negate
// all previous matchers.
</span><span class="macro">cfg_if! </span>{ @__apply cfg(all($(<span class="macro-nonterminal">$m</span>,)* not(any($(<span class="macro-nonterminal">$not</span>),<span class="kw-2">*</span>)))), $(<span class="macro-nonterminal">$it</span>)* }
<span class="comment">// Recurse to emit all other items in `$rest`, and when we do so add all
// our `$m` matchers to the list of `$not` matchers as future emissions
// will have to negate everything we just matched as well.
</span><span class="macro">cfg_if! </span>{ @__items ($(<span class="macro-nonterminal">$not</span>,)* $(<span class="macro-nonterminal">$m</span>,)<span class="kw-2">*</span>) ; $(<span class="macro-nonterminal">$rest</span>)* }
};
<span class="comment">// Internal macro to Apply a cfg attribute to a list of items
</span>(@__apply <span class="macro-nonterminal">$m</span>:meta, $(<span class="macro-nonterminal">$it</span>:item)<span class="kw-2">*</span>) =&gt; {
$(<span class="attribute">#[<span class="macro-nonterminal">$m</span>] </span><span class="macro-nonterminal">$it</span>)*
};
}
<span class="comment">// Helper macro for specialization. This also helps avoid parse errors if the
// default fn syntax for specialization changes in the future.
</span><span class="attribute">#[cfg(feature = <span class="string">&quot;nightly&quot;</span>)]
</span><span class="macro">macro_rules! </span>default_fn {
(<span class="attribute">#[$(<span class="macro-nonterminal">$a</span>:tt)<span class="kw-2">*</span>] </span>$(<span class="macro-nonterminal">$tt</span>:tt)<span class="kw-2">*</span>) =&gt; {
<span class="attribute">#[$(<span class="macro-nonterminal">$a</span>)<span class="kw-2">*</span>] </span>default $(<span class="macro-nonterminal">$tt</span>)*
}
}
<span class="attribute">#[cfg(not(feature = <span class="string">&quot;nightly&quot;</span>))]
</span><span class="macro">macro_rules! </span>default_fn {
($(<span class="macro-nonterminal">$tt</span>:tt)<span class="kw-2">*</span>) =&gt; {
$(<span class="macro-nonterminal">$tt</span>)*
}
}
</code></pre></div>
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